/***
 * ASM: a very small and fast Java bytecode manipulation framework Copyright (c) 2000-2011 INRIA,
 * France Telecom All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: 1. Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.googlecode.aviator.asm;

/**
 * A visitor to visit a Java annotation. The methods of this class must be called in the following
 * order: ( <tt>visit</tt> | <tt>visitEnum</tt> | <tt>visitAnnotation</tt> | <tt>visitArray</tt> )*
 * <tt>visitEnd</tt>.
 *
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public abstract class AnnotationVisitor {

  /**
   * The ASM API version implemented by this visitor. The value of this field must be one of
   * {@link Opcodes#ASM4}.
   */
  protected final int api;

  /**
   * The annotation visitor to which this visitor must delegate method calls. May be null.
   */
  protected AnnotationVisitor av;

  /**
   * Constructs a new {@link AnnotationVisitor}.
   *
   * @param api the ASM API version implemented by this visitor. Must be one of
   *        {@link Opcodes#ASM4}.
   */
  public AnnotationVisitor(final int api) {
    this(api, null);
  }

  /**
   * Constructs a new {@link AnnotationVisitor}.
   *
   * @param api the ASM API version implemented by this visitor. Must be one of
   *        {@link Opcodes#ASM4}.
   * @param av the annotation visitor to which this visitor must delegate method calls. May be null.
   */
  public AnnotationVisitor(final int api, final AnnotationVisitor av) {
    if (api != Opcodes.ASM4) {
      throw new IllegalArgumentException();
    }
    this.api = api;
    this.av = av;
  }

  /**
   * Visits a primitive value of the annotation.
   *
   * @param name the value name.
   * @param value the actual value, whose type must be {@link Byte}, {@link Boolean},
   *        {@link Character}, {@link Short}, {@link Integer} , {@link Long}, {@link Float},
   *        {@link Double}, {@link String} or {@link Type} or OBJECT or ARRAY sort. This value can
   *        also be an array of byte, boolean, short, char, int, long, float or double values (this
   *        is equivalent to using {@link #visitArray visitArray} and visiting each array element in
   *        turn, but is more convenient).
   */
  public void visit(String name, Object value) {
    if (av != null) {
      av.visit(name, value);
    }
  }

  /**
   * Visits an enumeration value of the annotation.
   *
   * @param name the value name.
   * @param desc the class descriptor of the enumeration class.
   * @param value the actual enumeration value.
   */
  public void visitEnum(String name, String desc, String value) {
    if (av != null) {
      av.visitEnum(name, desc, value);
    }
  }

  /**
   * Visits a nested annotation value of the annotation.
   *
   * @param name the value name.
   * @param desc the class descriptor of the nested annotation class.
   * @return a visitor to visit the actual nested annotation value, or <tt>null</tt> if this visitor
   *         is not interested in visiting this nested annotation. <i>The nested annotation value
   *         must be fully visited before calling other methods on this annotation visitor</i>.
   */
  public AnnotationVisitor visitAnnotation(String name, String desc) {
    if (av != null) {
      return av.visitAnnotation(name, desc);
    }
    return null;
  }

  /**
   * Visits an array value of the annotation. Note that arrays of primitive types (such as byte,
   * boolean, short, char, int, long, float or double) can be passed as value to {@link #visit
   * visit}. This is what {@link ClassReader} does.
   *
   * @param name the value name.
   * @return a visitor to visit the actual array value elements, or <tt>null</tt> if this visitor is
   *         not interested in visiting these values. The 'name' parameters passed to the methods of
   *         this visitor are ignored. <i>All the array values must be visited before calling other
   *         methods on this annotation visitor</i>.
   */
  public AnnotationVisitor visitArray(String name) {
    if (av != null) {
      return av.visitArray(name);
    }
    return null;
  }

  /**
   * Visits the end of the annotation.
   */
  public void visitEnd() {
    if (av != null) {
      av.visitEnd();
    }
  }
}
